Bump py from 1.5.3 to 1.10.0 in /backend

Bumps [py](https://github.com/pytest-dev/py) from 1.5.3 to 1.10.0.
- [Release notes](https://github.com/pytest-dev/py/releases)
- [Changelog](https://github.com/pytest-dev/py/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/py@1.5.3...1.10.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/requirements.txt

@@ -7,7 +7,7 @@ flask-sqlalchemy==2.3.2
 Flask-Migrate==2.1.1
 pymysql==0.9.3
 pytest==3.6.2
-py==1.5.3
+py==1.10.0
 pluggy==0.6.0
 pytest-cov==2.6.0
 gunicorn==19.7.1